1. Field of the Invention
The present invention relates to a method of dot-printing underlines and particularly, to an improved method of dot-printing underlines below printed letters, symbols and the like.
2. Description of the Prior Art
There is well-known such a dot printer comprising a print head reciprocatable relative to a recording paper, the print head including a single or plural dot pins which are driven and impacted against the recording paper sequentially in accordance with print commands for a given letter, symbol or the like to form a dot matrix recording corresponding to the given letter on the paper. Particularly, such a print head including a plurality of dot pins arranged to provide a plurality of print rows simultaneously is practically utilized in a high-speed shuttle type dot-line printer.
In such a type of dot printers, each dot pin is driven in accordance with a character font to provide prints such as ordinary letters and the like, for example. There is therefore a relatively large rest time between each adjacent printing actions of the individual dot pin. Driving means or normally solenoid means for each dot pin is of such an operative capacity that anticipates the rest time between each adjacent printing actions. Voltage drop in the power supply also is maintained to a proper value on such conventional printing actions.
Recently, a printer has been proposed which has an additional function as relatively long range continuous printing, for example, printing underlines below printed characters or printing a table. For such an additional underlining function, the dot pin drive must continuously be supplied with drive current. In the prior art systems, this raised a problem in that the power supply required to drive the underlining dot pins did not have enough capacity to prevent the voltage drop, resulting in faulty quality of printed letters.
To overcome such a problem, the prior art systems require a large-capacity power source. This would provide increased dimensions and costs.